During the week of 23rd October, I attended a conference here in Australia run by the Cancer Council of Western Australia. The keynote speaker was Associate Profession Eva Schernhammer from Harvard Medical School where she is Associate Professor of Medicine and Epidemiology, as well as holding adjunct faculty positions at the Department of Epidemiology Fielding School of Public Health, UCLA and the Department of Epidemiology at the University of Vienna where she gained her graduate degree.
Over the past 10 years she has levied almost 10 million research dollars from NIH related to her primary interest in the relationship of circadian rhythms and melatonin to cancer risk. This work has led to the establishment in 2007, of a new classification by the World Health Organization, of shift work as a probable human carcinogen - which means that working nights over a long period of time can be a part of the process that leads to the development of cancer.
Her lecture at the conference was based around the findings of the world renowned Nurses Health Study which has been an ongoing Epidemiological research tool since its inception in 1976 - a study which has a definite Aussie flavour as one of the founding “fathers” of that study was Frank Speizer, now Distinguished Professor of Medicine at Harvard Medical School. The original Nurses study recruited 121,700 nurses, and has followed them ever since with a two yearly questionnaire that still evokes a 90% response rate - a truly remarkable achievement! Initially, the researchers looked at things like the oral contraceptive pill which back then had only been commercially available for around 10 years, and was significantly stronger than the more modern combinations. They also looked at smoking, hormone replacement therapy and odd things such as hair dyes, to see if there was any link to specific health issues or risks of cancer.
In 1991, they added a dietary questionniare to their list of inquiries, and in 1993 Quality of Life was added and then in the 1990’s they started to collect blood and urine samples which are still stored in hundreds of refrigerators in the basements of their building at Harvard!
In other words they have amassed a massive amount of information which the epidemiologists have continued to crunch ever since. Many of their findings have subsequently impacted on Government Health Policies around the world, and more information will help refine our understanding of the interaction between the human body and the environment in which we live.
Cigarette smoking has been known to lead to various cancers since the mid 1960’s and this has been confirmed by the Nurses Study in women too. But it’s in the area of diet and obesity that the study has had a particular impact.
A diet rich in red or processed meat raises the risk of getting cancer.
Obesity raises the risk of breast cancer, although interestingly, if a woman loses weight after the menopause she will reduce her risk of breast cancer.
When they looked at causes of becoming overweight, the findings showed that eating potatoes, processed grains and red and processed meat were all implicated in stacking on the kilos. But a diet high in vegetables, salads, nuts and even yoghurt would help keep those kilos off.
When it comes to reducing the risks of developing cancer in women, the Nurses study showed that:
Maintaining a good level of effective physical activity reduced cancer rates as did decreasing the amount of red and processed meat in the diet. Other factors which point to lower risks of developing cancer in women included being lean at ages 5 and 10 years and avoiding alcohol during adolescence. These last two facts need to reach consciousness in all western parts of the world where childhood obesity is such an increasing challenge, and teenage drinking is at almost epidemic proportions.
Rates of fertility were also looked at in relation to women’s weights: so having a Body Mass index between 20 and 24 was favourable for fertility, but on either side of that range, levels of fertility dropped away.
When it came to skin cancer, it’s generally thought that all sunburns are created equal and were equally dangerous. But it appears that in women at least, if you have blistering sunburns between the ages of 15 and 20 then you double the rate of risk for developing a malignant melanoma. And blistering sunburns, although very painful, were less significant after the age of 30, although they are still associated with other forms of skin cancers such as basal cell cancers and squamous cell cancers. The message here is that once again we have to remind our bullet proof teenagers that alcohol and sunshine are not as great for us as the advertisers would like us to think they are.
On the up side for this now aging cohort of Nurses is the finding that the long term usage of Aspirin - greater than 20 years according to the study - is associated with a reduced incidence of colon cancer. However, before you start thinking of taking long term aspirin, you need to talk it over with your family physician, because aspirin may have been around forever, but it too has it’s drawbacks and certainly is not for everyone.
Finally Prof Schernhammer spoke briefly about her personal research into the cancer causing effects of shift work.
As we all know, we all need sleep and one of the major players in the sleep cycle - or circadian rhythm - is melatonin which is produced and released by the pineal gland in the brain. When there’s lots of light around Melatonin production is suppressed and there is a compensatory increase in the amount of Oestrogen produced, and it is thought that this process may play a part in the increased rates for cancer to be found amongst shift workers. Across the board, Professor Schernhammer has found a 50% increase in the rate of cancers in long term shift workers.
Naturally this needs to be addressed, and their focus now is on ways of how to reduce those risks by varying the type, frequency and amount of shift work that an individual should do. And perhaps there might be a place to think of more appropriate lighting for certain workers - needless to say there is much work and research to be done, but now at least it has been recognized by the World Health Organization as a real risk for developing cancer.
The other keynote talk was by Assistant Professor Markus Frank also from the US and who is an expert in the field of Cancer Stem Cell biology. This was a really fascinating talk, but very scientific in it’s detail. What I gleaned from this very interesting man was, just like we humans, not all cancer cells are created equal either.
If you think of a cancer anywhere in the body, we have the image of “malignant” cells - nasty things just out to do us no good - a bit like a gang on the street. But not all gang members are really toxic or virulent, there’s usually a few ringleaders who stir up the most anger and cause the most damage, and it’s always best to target the ringleaders in order to control the situation. And it’s the same with cancers - Cancer Stem Cells are the ringleaders and the ones that we really need to focus on. Most cancer treatments do kill off cancer cells, but they don’t kill off the cancer stem cells and that’s why we get recurrences. The trouble is that it’s much harder to kill these cells off than you’d think. I actually sat there thinking, “how come these microscopic individual cells avoid and defeat the best - not only that our own immune system can throw at it - but the combined brain power of the best thinkers and computers that we have at our disposal!” It’s as mind baffling as it is frustrating.
The good news is that researchers are developing several approaches to target these cells and develop specific treatments based on the cancer stem cells DNA, their surface markers and their ability to generate their own blood supplies. It’s early days in the science of Cancer Stem Cells but already effective treatments are appearing in laboratory models. The battle has only just begun.
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